Communication of motion by contact or impulse was treated as the paradigm a priori intelligible causal connection.

We believe that Hume’s discussion of the communication of motion by contact or impulse shows his debt to Newton especially clearly. In section 7, part 1 of the Enquiry Hume is criticizing the inherited ideas of necessary connection. We believe that both here and in section 4, part 1, where he rejects any a priori demonstration of causality, Hume is centrally concerned with the conception of necessary connection articulated by the mechanical natural philosophy. This philosophy had taken the commu